Researchers discovered fossilized ink in the sacs of an ancient squid. The 160-million year-old ink is the oldest ever found and researchers were able to analyze the melanin in the ink, which gives it its black pigment, and shed light on the evolutionary path of cephalopods, such as squid, octopus and cuttlefish.

"Though the other organic components of the squid we studied are long gone, we've discovered through a variety of research methods that the melanin has remained in a condition that could be studied in exquisite detail," John Simon, study author and chemistry professor at the University of Virginia, said in a statement.

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Researchers compared the ancient ink to the ink in modern squids and found that both are almost identical to each other, meaning that the animals have evolved very little since the Jurassic period, which surprised the researchers.

"It's close enough that I would argue that the pigmentation in this class of animals has not evolved in 160 million years," Simon said. "The whole machinery apparently has been locked in time and passed down through succeeding generations of squid. It's a very optimized system for this animal and has been optimized for a long time."

The research shows that organic matter can survive fossilization, researchers said. Usually organic matter, such as protein or animal tissue, is broken down during fossilization, leaving only the skeleton behind. This study shows that some things other than bone can survive.

Cephalopods use ink to distract their enemies and make a quick escape. The findings suggest that the technique works very well, according to the study, published Monday in the journal Proceedings of the National Academy of Sciences.

"It's close enough that I would argue that the pigmentation in this class of animals has not evolved in 160 million years," Simon told MSNBC. "The whole machinery apparently has been locked in time and passed down through succeeding generations of squid. It's a very optimized system for this animal and has been optimized for a long time."